Internet protocol collaborative mobility

ABSTRACT

Systems and methods are provided for maintaining communications with mobile users within organizational logical network groups when transitioning between logical groups. A client mobility agent resides as part of a mobile communication unit and monitors link metrics to determine if a transition to another logical network group is desired. The client mobility agents and a server mobility agent collaborate to reassign or re-home a mobile communication unit to a new home logical network group, and provide the mobile communication unit with a new group address upon entering a new logical network. The server mobility agent collaborates with a server mobility agent of the previous logical group that the mobile communication unit was a member to transfer sessions and services associated with the mobile communication unit to the new logical network.

TECHNICAL FIELD

[0001] The present invention relates to communications and, moreparticularly, to membership transitions of mobile communication unitsbetween logical network groups.

BACKGROUND OF THE INVENTION

[0002] The use of communication systems having wireless mobilecommunication units has become widespread. Wireless communicationsystems provide several important advantages over conventional wiredsystems. For example, wireless communication users can communicate inlocations where wired service is not available or feasible, such asremote or rugged locations. Additionally, wireless communication usershave much more mobility because they do not have to connect to a fixedwired network. These and other favorable characteristics make wirelesscommunications ideally suited for personal, business, military, searchand rescue, law enforcement, and water vehicle applications. The powerof networking and collaborative, distributed computing is being realizedin wireless mobile communication units. However, mobile networks providemany additional challenges not associated with fixed networks.

[0003] Several important mobility management issues need to be addressedin designing a communication system with a dynamic network topologyhaving mobile access points and/or mobile network nodes with arelatively large number of mobile users. Critical issues with mobilemanagement include tracking mobile users in the system, reaching andinitiating communications with mobile users and continuity of servicewhen a mobile user moves between coverage areas. Conventional networksdo not provide solutions to these problems within their specificdomains. In conventional systems, a network administrator needs toreconfigure the respective networks and/or networks to accommodate theentry of a new mobile user. For example, if a user moves a laptopcomputer from a first network to a second network, the second networkwill need to be reconfigured to assign a new address (e.g., (InternetProtocol (IP) address) to the laptop computer to accommodate for thedomain name associated with the laptop. A system administrator will haveto then enter the domain name into the domain name server (DNS) for thesecond network and remove the domain name from the DNS of the firstnetwork. Both the first network and second network will then have to berebooted to complete the configuration.

[0004] In mobile network environments, capabilities are required forallowing nomadic users to migrate from one logical network orsub-network to other logical networks or sub-networks without humaninteraction or network management interactions. Current solutionsinclude Cellular Digital Pack Data (CDPD) networks, Cellular/PersonalCommunications Services (Cellular/PCS) systems, and Mobile InternetProtocol (mobile IP) networks. These solutions provide mobile users withfixed addresses or identifications and employ third party services toforward information destined for the mobile unit through one or moreintermediaries to the network that the mobile user currently resides.

[0005] For example, mobile IP networks include mobile nodes, home agentsand foreign agents. A home agent is a router that authenticates a mobilenode, tracks a mobile user location and redirects data packets to themobile user's current location. A foreign agent assists the mobile nodein informing its home agent of its current location and routes datatraffic sent by the mobile user. Similar to CDPD, mobile IP usestriangular routing. A mobile's home agent receives packets destined tothe home address of the mobile user, encapsulates the packet andtransmits the packet to the mobile node that the mobile user iscurrently residing. A mobile user must contact home in order to receiveany services (e.g., e-mail, voice). The home agents are built into thenetwork layer of a Transmission Control Protocol/Internet Protocol(TCP/IP) stack, and therefore, burdens the overhead associated with thenetwork layer.

[0006] Additionally, the use of a home agent or third party service isimpractical in some applications due to certain limitations. Forexample, recently the introduction of distributed denial of service(DDS) has become available to protect against users trying to accessother user's systems and invoke destructive programs with fictitiousnames and addresses from the other user's system. Ingress filters detectpackets launched with IP addresses not part of the transmitting packetand terminate this action. This terminates a mobile IP transmissionsince the mobile IP sent from the mobile user is foreign to the ingressfilter. Furthermore, mobile IP is impractical for mobile tacticalnetworks, since the node having the home agent can be destroyedeliminating any communication to the mobile node when it is at avisiting node.

SUMMARY OF THE INVENTION

[0007] The following presents a simplified summary of the invention inorder to provide a basic understanding of some aspects of the invention.This summary is not an extensive overview of the invention. It isintended neither to identify key or critical elements of the inventionnor delineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

[0008] The present invention relates to systems and methods formaintaining communications with mobile users within organizationallogical groups (e.g., logical networks, subnetworks) when transitioningbetween logical groups. The present invention includes client mobilityagents that reside in mobile communication units (MCUs) that collaboratewith server mobility agents that are provided as part of networkservices of logical network groups. The client mobility agents andserver mobility agents collaborate to reassign or re-home a mobilecommunication unit (MCU) to a new home logical network group and providethe MCU with a new group address upon entering a new logical network.The client mobility agent monitors link metrics (e.g., sourceaddressing, link quality, bit-error rate, access point information) todetermine if transition to another logical network group is desired. Theclient mobility agent requests a new logical group address (e.g., IPaddress) upon determining to transition to a new logical group.

[0009] The new logical address is provided by network services of thenew logical group. The network services can be commercial off-the-shelf(COTS) software and hardware services that provide the desired newlogical group address, associate a domain name with the new logicalgroup address, and replicate the domain name and associated new logicalgroup address to other network connected to the new logical group. Uponreceipt of the new logical group address, the client mobility agentcollaborates with the server mobility agents to invoke a transfer ofinformation associated with the mobile communication unit. A servermobility agent of the new logical group collaborates with a servermobility agent of an old logical group from which the MCU istransitioning to have services (e.g., e-mail, phone) transferred to thenew logical network group. Additionally, current communication sessions(e.g., Voice Over Internet Protocol (VOIP), Video) are transferred fromthe old network to the new network by collaboration between the newlogical group server mobility agent and the old logical group servermobility agent to provide minimal disruption during a communicationsession. The current communications sessions are transferred prior toassignment of the new logical group address. The mobility functionalityexecutes above the session layer without burdening the network layer ofa TCP/IP or OSI network model.

[0010] In one aspect of the present invention, user mobility is providedusing collaboration between intelligent mobility agents and standardTCP/IP suite network services. The TCP/IP suite services includeLightweight Directory Access Protocol (LDAP) Directory Services (DS),Domain Name Service with Dynamic Update or Dynamic Domain Name Server(DDNS), and Dynamic Host Configuration Protocol (DHCP). LDAP DS is acomputer service that enables users to modify and access informationstored in a computerized directory. DDNS (RFC 2136), part of a directoryservices that pairs domain names with IP addresses, enhances standarddomain naming with the ability to dynamically update zone files keepingnaming services current without requiring servers to be restarted. DHCPleases IP address to hosts when entering a domain and manages IP addresswhile a host continues to operate in the domain. The TCP/IP suiteservices are provided as part of the available network services of alogical network group.

[0011] To the accomplishment of the foregoing and related ends, certainillustrative aspects of the invention are described herein in connectionwith the following description and the annexed drawings These aspectsare indicative, however, of but a few of the various ways in which theprinciples of the invention may be employed and the present invention isintended to include all such aspects and their equivalents. Otheradvantages and novel features of the invention will become apparent fromthe following detailed description of the invention when considered inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 illustrates a block diagram of a wireless communicationsystem having client mobility agents and server mobility agents inaccordance with an aspect of the present invention.

[0013]FIG. 2 illustrates a MCU transitioning between network servers ina “Break-before-Make” mode in accordance with an aspect of the presentinvention.

[0014]FIG. 3 illustrates a MCU transitioning between network servers ina “Make-before-Break” mode in accordance with an aspect of the presentinvention.

[0015]FIG. 4 illustrates a block diagram of a MCU in accordance with anaspect of the present invention.

[0016]FIG. 5 illustrates a particular implementation of a clientmobility agent in accordance with an aspect of the present invention.

[0017]FIG. 6 illustrates a functional block diagram of a network serverin accordance with an aspect of the present invention.

[0018]FIG. 7 illustrates a service block diagram in accordance with anaspect of the present invention.

[0019]FIG. 8 illustrates a state diagram for transitioning a MCU betweenlogical networks in accordance with an aspect of the present invention.

[0020]FIG. 9 illustrates a block diagram of a wireless communicationsystem having access points in accordance with an aspect of the presentinvention.

[0021]FIG. 10 illustrates a flow diagram of a methodology fortransitioning MCUs between logical groups in accordance with an aspectof the present invention.

[0022]FIG. 11 illustrates a flow diagram of a methodology for executingnetwork services for transitioning MCUs between logical groups inaccordance with an aspect of the present invention.

DETAILED DESCRIPTION OF INVENTION

[0023] The present invention provides for systems and methods formaintaining communications with mobile users within organizationalgroups (e.g., logical networks, subnetworks) when transitioning fromgroup to group. Communication is maintained automatically andtransparent to any human user interaction. The present inventionprovides a user mobility mechanism that operates completely above thesession layer and without burdening the network layer with the trackingand location of mobile users. Intelligent mobility agents are providedin both logical network servers (server mobility agents) and MCUs(client mobility agents). The client mobility agents and server mobilityagents collaborate to reassign or re-home a MCU to a new home group andnew IP address upon entering a new logical network. The intelligentmobility agents can employ COTS software and hardware services toprovide the desired mobility functionality above the session layers.

[0024] Groups consist of collections of users sharing communications,network services, and exist in the same relative geo-location.Connectivity within a group will be a combination of wireless and wiredlinks forming a logical network or subnet within the greater network.The group operates as a flat network for all elements participating.Addressing is a single logical network or subnet of an IP address.Client addresses for the group are distributed dynamically within thegroup. Group participants will acquire a group address upon entering thegroup. Legacy systems having addressing fixed or determined by othermechanisms will cooperate through group routing. The group enablesaccess, for connectivity to other groups, by providing gateways to anetwork backbone.

[0025] In the following description, for purposes of explanation,numerous examples are set forth in order to provide a thoroughunderstanding of the present invention. It may be evident, however, thatthe present invention may be practiced in other examples not set forthin the following description. In other instances, structures and devicesare shown in block diagram form in order to facilitate describingvarious aspects of the present invention.

[0026]FIG. 1 illustrates a mobile communication system 10 comprising aplurality of logical networks or subnetworks 16, 28 and 40 coupled to anetwork backbone 14 to form a parent network 11 (e.g., internet,intranet). It is to be appreciated that the communication system can becomprised of one or more hierarchical levels of networks. The networkbackbone 14 can be a hardwired data communication path made of twistedpair cable, shielded coaxial cable or fiber optic cable, for example, orwireless (e.g., an adhoc backbone) or partially wireless in nature.Communications between logical networks are provided by a respectivenetwork server that establishes logical connections between therespective logical networks across the network backbone 14. The networkserver of a respective logical network provides network services for itsrespective network.

[0027] In one aspect of the invention, the network services includeTCP/IP suite services, such as DDNS, DHCP and LDAP DS. The networkservices can be provided across a plurality of network devices or resideon a single network device. A primary domain controller providesadministrative control of the network services for a respective logicalnetwork.

[0028] The intelligent mobility agents of the present invention supporttwo modes of operations to facilitate continuous communication. Thefirst mode is referred to as “Break-before-Make” mode, which supportsthe conditions where a user transitions between two groups and is notable to maintain continuous link connectivity. In this mode, continuoussession operation is not achievable due to lack of physical connectivityhowever, upon entry to a new group the user is able to communicate withthe new group and source connections with the entire network. The secondmode is referred to as the “Make-before-Break” mode and supports theconditions where a user transitions between two groups and maintainsphysical link connectivity to both groups for a short period. Acontinuous Transmission Control Protocol/User Datagram Protocol(TCP/UDP) session operation is maintained as the user transitions fromone group to another. The present invention provides user mobilitymechanisms to migrate the users affiliation to a new group without userassistance or interruption (e.g., system restart) of communicationequipment operation.

[0029]FIG. 2 illustrates a “Break-before-Make” mode where a MCU 68having a client agent 70 is a member of a first logical group with afirst network server 60 having a server agent 62. The MCU 68 has a firstposition 72 in which the MCU 68 is in a communicative relation withmembers of the first logical group and the network server 60. The MCU 68then moves from the first position 70 to a second position 74 in whichis not able to maintain a link with the network server of the firstlogical group and does not have any link connection to any other logicalgroups. The MCU 68 then moves from the second position 74 to a thirdposition 76 in which the MCU 68 establishes a new logical connectionwith a second network server 64 having a server agent 66 in a secondlogical network. The client mobility agent 70 and the server mobilityagents 62 and 66 can collaborate to provide membership of the MCU in thesecond logical group and remove the MCU from membership in the firstlogical group.

[0030]FIG. 3 illustrates a “Make-before-Break” mode where a MCU 88having a client agent 90 is a member of a first logical group with afirst network server 80 having a server agent 82. The MCU 88 has a firstposition 92 in which the MCU 88 is in a communicative relation withmembers of the first logical group and the network server 90. The MCU 88then moves from the first position 92 to a second position 94 in whichlink connectivity is provided from the first logical group in additionto a second logical group with a second network server 84 having aserver agent 86. The MCU 88 then moves from the second position 94 to athird position 96 in which the MCU 88 logical connection with the firstlogical network is lost. The MCU 88 then determines that the MCU 88 willjoin the second logical network. The client mobility agent 80 and theserver mobility agents 82 and 86 can collaborate to provide membershipof the MCU in the second logical group and remove the MCU frommembership in the first logical group.

[0031] In one aspect of the invention, a common “identity” for themobile user is maintained by utilizing standard network location DomainName Service (DNS) to locate the mobile user anywhere in the network.The user mobility mechanisms support any voice, video, or datacommunications. The user mobility mechanisms support both wireless andwired operation.

[0032] Referring again to FIG. 1, a first logical network 16 includes anetwork server 18, a second logical network 28 includes a network server30 and a third logical network 40 includes a network server 42. Aplurality of MCUs are associated with the logical networks 16, 28 and40. The MCUs can move between logical networks and be re-homed employingthe intelligent homing agents in accordance with the present invention.The first logical network 16 has a first MCU member 22 and a second MCUmember 26. The second MCU member 26 has moved outside the range of thefirst logical network 16 and has entered a “Break-before-Make” mode. Thesecond logical network 28 has a third MCU member 32 and a fourth MCUmember 36. The fourth MCU member 36 has moved within the range of boththe second logical network 28 and the third logical network 40, suchthat the fourth MCU member 36 is receiving link connectivity from bothnetworks, and therefore, has entered a “Make-before-Break” mode. Thethird logical network 40 has a fifth MCU member 44 and a sixth MCUmember 46. Each network server 18, 30 and 42 include a server mobilityagent (SA) 20 and each MCU includes a client mobility agent (CA) 24. Theserver mobility agents 20 and the client mobility agents 24 collaboratewith one another to re-home MCUs as they move from one logical networkto another.

[0033] The client mobility agents 24 monitor link metrics to determinewhether to become a member in a new logical network or retain membershipin a logical network. If the client mobility agent determines to join anew logical network, the client mobility agent initiates coordinationwith the new server mobility agent 20 to transfer current opencommunication session information to the new logical network. The clientmobility agent then invokes a request for a new IP address to beassigned to the MCU. The new IP address can be provided using standardavailable services such as DHCP. Once the client mobility agent receivesthe new IP address, the new IP address can be associated with the MCUdomain name using DDNS. The domain name and IP address can be replicatedacross the network utilizing directory services such as LDAP DS. Theclient mobility agent then initiates coordination with the new servermobility agent 20 to transfer services (e.g., e-mail, phone) associatedwith the MCU from the old network to the new network.

[0034] The primary responsibility for initiating user migrationdetection and re-homing is within the mobile client, in the form of theclient mobility agent. FIG. 4 illustrates a functional block diagram ofa MCU 100 having a client mobility agent 102 in accordance with anaspect of the present invention. FIG. 4 illustrates the interactionsbetween the client mobility agent 102, a client operating system (OS)110 and a wireless link connectivity component 112 (e.g., sessionlayer). The client mobility agent 102 includes a link monitor 104. Thelink monitor 104 monitors link metrics (e.g., source addressing, linkquality, bit-error rate, access point information) within the currentlogical network or group. The wireless connectively component 112 cansignal a loss of service and return to service when connectivity is lostand reestablished (e.g., Break-before-Make). The link monitor 104 thendetermines whether a logical network or group change has occurred bysampling the source address traveling on the current network via thewireless link connectivity component 112.

[0035] Alternatively, the link monitor 104 can monitor other linkmetrics such as signal quality of one link from a first network and asecond link from a second network when connectivity is establishedbetween two or more logical networks (e.g., Make-before-Break). Ineither situation, the link monitor 104 can determine if a transitionbetween logical networks is desirable based on one or more link metrics.If a transition between networks is desirable, the network initializer106 initiates a client agent and server agent coordination routine 108,which communicates to the new network server via the wireless linkconnectivity component 112 relating to the transferring of currentcommunication sessions that the MCU is associated with at the previousnetwork. The link monitor 104 transmits a new network request thatinvokes a network initializer 106. The network initializer 106 initiatesan address request command through an OS command line (e.g., API) to theclient OS 110. The client OS 110 then invokes an address release andrequest. The address release and request is provided through thewireless link connectivity component 112 to the network servicesresiding on a network server (not shown).

[0036] The address release and request can be provided employing DHCPwith Intragroup updates occurring utilizing LDAP DS. For example, DHCPreleases an old IP address and issues a new IP address which causes DHCPupdates to a user's LDAP DS record, through an LDAP exchange, to reflectthe new IP address and re-home the user to the new local network orgroup. The LDAP DS then provides replication of the new IP addressthroughout the other logical networks or groups. Once the MCU 100receives its new assigned IP address, the network initializer 106initiates the client agent and server agent coordination routine 108,which communicates to the new network server via the wireless linkconnectivity component 112. The server agents of the old network and newnetwork cooperate to transmit information relating to current servicesthat the MCU is associated with at the previous network. The MCU cancommunicate in the new group while server mobility agents initiateIntergroup updates (e.g., service transfers) to the MCUs new logicalnetwork location.

[0037]FIG. 5 illustrates a MCU 120 having an exemplary client mobilityagent (CA) 127 implementation in accordance with an aspect of thepresent invention. The CA 127 is a machine level entity that stands infor a human user and executes the activity necessary to re-home the MCU120 to a new logical network or group without requiring human userinteractions. The CA 127 is an autonomous agent, resident in the client(MCU 120), which identifies changes in location and executes machinelevel commands, to affect the MCU 120 migration from one logical networkto another.

[0038] The CA 127 is a link monitor that includes a filter driver 128, afilter Dynamic Link Library (DLL) 130 and a CA network service processcomponent 132. The filter driver 128 handles the low level requests forstatistical data from a wireless Local Area Network (LAN) card 122through an application program interface (API) 126 and a LAN driver 124.The network service process component 132 executes in the background andanalyzes the data returned from the filter driver 128 to decide when tore-associate with a new subnet. The CA 127 monitors the association tothe current logical network by polling the status of the client LAN card122. This can be accomplished by monitoring an associated access pointand its logical network, link connectivity source addresses, signalquality or a number of other link metrics. When detecting newassociations, the CA network service process component 132 initiates aDHCP release and renew to obtain an IP address for the new association.

[0039] The CA filter driver 128 is an upper filter driver residing abovethe LAN device driver 124. The CA filter driver 128 captures 10 RequestPackets (IRP's) generated by the CA 127. The network service portion 132of the CA 127 is a background service process analyzing the datareturned from the filter driver 128 and implementing various states,such as initiations of DHCP release/renew and server agent coordination.The CA filter DLL 130 manages the interface to the CA filter driver 128and runs as a background process. Alternatively, a daemon can beemployed instead of a DLL based on the operating system being ultilizedat the MCU 120. The DLL 130 performs actions based on predefinedcriteria. The filter driver 128 communicates through the LAN driver 124to obtain the results indicated by the code contained in the IRP's. Thenetwork service portion 132 of the CA communicates through the DLL 130,to the filter driver 128, obtaining status information from the wirelessLAN card 122. The DLL 130 uses the data to determine when to initiate anoperating system DHCP release and renew cycle. Once the IP address isrenewed, a SA coordination routine is invoked, and the client processreturns to monitoring of the wireless LAN card 122.

[0040]FIG. 6 illustrates a functional block diagram of a network server140 having a server mobility agent 142 in accordance with an aspect ofthe present invention. The server mobility agent 142 communicates withthe client mobility agent to perform a variety of functions inaccordance with the present invention. The network services 154 receivea request for a new address (e.g., IP address) through a wireless linkconnectivity component 152 from a client mobility agent when a MCUdetermines that it desires to enter a new logical network or group. Inone aspect of the invention, the network services 154 receive a newaddress request in the form of a DHCP request and release through thewireless link connectivity component 152. DHCP releases the old addressand issues a new IP address to the client agent through the wirelesslink connectivity component 152. DHCP then invokes LDAP DS residing inthe network services 154 to inform other groups of the MCUs new IPaddress. The LDAP DS then provides replication of the new IP addressthroughout the other logical networks or groups via a backbone networklink connectivity component 156. The LDAP DS then interacts with a DDNSservice in the network services 154. The network services 154 manageuser traceability by maintaining the current IP address associated withthe user's domain name across both local and wide area environments.

[0041] Once the MCU has been assigned a new IP address, the networkserver 140 receives an initialization to a client agent and server agentcoordination routine 144 via the wireless link connectivity component152. The client agent and server agent coordination routine 144 receivesinformation relating to associations of the MCU at the previous network.The client agent and server agent coordination routine 144 then invokesa server agent to server agent coordination routine 146. The serveragent to server agent coordination routine 146 is provided withinformation relating to the MCU, which includes information relating tothe group or logical network that the MCU was previously a member, theprevious IP address, current session information and current availableservices (e.g., e-mail, phone).

[0042] The server agent to server agent routine 146 establishes aconnection between the network server of the new group and the old groupthrough the backbone network link connectivity component 156. If acurrent session is in progress, the server agents transfer the currentsession before the CA releases the IP address of the old logical networkusing a transfer session component 148 of the new and/or the old logicalnetwork server. The server mobility agent 142 then transfers servicesfrom the old logical network to the new logical network using a transferservices component 150 of the new and/or the old logical network server.For example, the transfer services component 150 of the new network canbuild a new electronic mailbox, and be operative to receive messagesfrom the old mailbox of the old network. The transfer services componentof the old network can be adapted to disassemble the old mailbox, andtransfer any messages to the new mailbox of the new network.

[0043]FIG. 7 illustrates a service block diagram 180 relating tointeraction between a MCU 182 and a network server (NS) 184 inaccordance with an aspect of the present invention. The MCU 182 includesa user man machine interface (MMI) 188 coupled to a client operatingsystem (OS) 190 to allow a user to provide communication to and from theclient operating system 190. The MCU 182 includes a client mobilityagent (CA) 186. The client mobility agent 186 monitors link metricsthrough a local network link connectivity component 192. The clientmobility agent 186 determines whether or not to enter a new networkbased on the monitoring of the link metrics. If the client mobilityagent 186 determines it wishes to enter a new network, a command isissued to the client operating system for a DHCP request and release.The client OS 190 then initiates a DHCP exchange through the localnetwork link connectivity component 192 to a DHCP service 200 residingon the network server (NS) 184. The DHCP exchange re-affiliates the hostwith the new domain, obtains an IP address, and updates the LDAP DSusing directory services 202.

[0044] The client operating system then initiates a DNS registration viaa DDNS service 198 through the local network link connectivity component192, which causes the LDAP DS to interact with DDNS services 198 toupdate a DNS table repository. The LDAP DS or directory services 202detects the DNS table repository update and replicates the DNS tablerepositories of other groups via replication in the intranet using thebackbone network link connectivity component 196. The managing of theuser traceability is maintained by associating the current IP addresswith the user's fully qualified domain name (FQDN) and enunciating ausers location, via DDNS, across both local and wide area environments.

[0045] Once the client has completed the client initiated DNSregistration, the CA 186 initiates a client agent to server agentcoordination routine between the CA 186 and a server mobility agent (SA)194. The SA 194 receives information relating to the old network fromwhich the MCU was a member and establishes a SA to SA group coordinationroutine through the ad-hoc backbone network link connectivity component196. If the migrate operation is a “Make-before-Break”, the SA to SAgroup coordination routine affects the transfer of current TCP and UDPsessions of the MCU from the old network to the new network prior todisconnecting from the old group. The SA to SA group coordinationroutine also affects the transfer of services (e.g., e-mail, phone) tothe new network. The CA then returns to monitoring link metrics, whilethe SA returns to monitoring the invocation of a CA to SA coordinationroutine.

[0046] The present invention can achieve collaboration between the userand standard services by employing intelligent agents (both client andserver based) operating above the session layer without disturbing thenetwork layer. The approach of the present invention requires nomodification to network layer routing and supports both unicast andmulticast operations. End point host hardware, operating system,networking software and application software remain unchanged with theaddition of intelligent mobility agents added to mobile users providethe necessary mobility services, requiring no man-in-the loop restart orother management of a host.

[0047] Agents (both client and server agents) replace man-in-the-loopoperations (restart or interactive management) by detecting migrationevents and initiating DHCP re-affiliations (without powering down thehost), managing parameter updates, and executing service migrations.User communications are continuous and tracking from location tolocation is intrinsic within the standard services, so, a user is alwaysfindable by other entities (users, SA functions, network management andsecurity function, etc.). The mobility agents enable collaborationbetween the standard services, client operating systems, and serveroperating systems. LDAP DS applications support both local and wide areauser migrations by providing unique user traceability through StandardFully Qualified Domain Name (FQDN) definitions. Current LDAP DSimplementations allow dynamic update capabilities through LDAP with astandardized network protocol.

[0048] Each group provides the network services supporting the logicalnetwork or subnet for the group. The group network services support allmobile users, referred to as clients, in the group. Intelligent serveragents, resident in the group network services, coordinate mobile usermigrations to or from the group with other groups for notification tothe larger network or internet. The mobile client or MCU is responsiblefor initiating mobility processes associated with transitions to or froma group. Intelligent client mobility agents, resident in the mobileuser, detect and sequence the transition of a client from one group toanother. Client mobility agents also coordinate with server mobilityagents to affect transfers of email and/or phone services, maintaincontinuous TCP/UDP sessions, and manage notification within the greaternetwork as to the client's location.

[0049] All of the user mobility activity relies on network and linklayers to provide transport of information, however, migration decisionsand re-homing of a client does not rely on modification of standardnetwork and link layer protocols. The present invention provides themobility task out of the network and link layers. The present inventionutilizes the application through session layers for managing, tracking,and migrating users with transparent (no user interaction required afterinitial login) operations. The intelligent mobility agents can utilizeindustry standard protocols and APIs to interface with COTS operatingsystems and network services forming the collaboration between thecommercial components. Routing protocols represent no constraints thataffect the ability to migrate and track users.

[0050]FIG. 8 illustrates a state diagram 220 of an intelligent agentmobility collaboration routine in accordance with an aspect of thepresent invention. The state diagram begins at a link monitor state 222where monitoring of link metrics is performed. If the link is stable,the state diagram repeats the link monitoring state 222. If the link isdropped or link metrics is detected from one or more additionalnetworks, the state diagram proceeds to a network detection state 224.At the network detection state 224, decisions are rendered about whetherthe mobile client should register at the new network. For example, ifthe link is dropped and the link is now detected in a different network,the mobile client would proceed to enter the new network. Alternatively,if link activity is detected from a second network, the networkdetection state would determine if the signal quality of the secondnetwork has reached a threshold level that would make it desirable forthe mobile client to enter the second network. Additionally, linkmetrics can be performed through access points. The mobile client wouldremain in the current network if the new access point was in the currentnetwork or choose to enter a new network if the access point was amember of the new network.

[0051] If the decision to remain in the network is made at the networkdetection state 224, the state diagram returns to the link monitor state222. If the decision is made to enter a new network, a decision is madewhether the transfer was a “Break-before-Make” transfer or a“Make-before-Break” transfer. If the transfer is a “Make-before-Break”transfer, the state diagram moves to an initiate SA coordination state230. The initiate SA coordination state 230 invokes a session migrationstate 232 at the server agent and invokes a DHCP initiate state 226. Ifthe transfer is a “Brake-before-Make” transfer, the state diagram movesdirectly to the DHCP initiate state 226. The DHCP initiate state 226releases the old IP address and assigns a new IP address, which isprovided into the DNS table repository by dynamic editing. The DHCPinitiate state 226 then advances to perform a LDAP state 228 andinitiate a SA coordination state 230. The LDAP state 228 replicates thenew address of the mobile client domain name to other networks, andreturns to the initiate SA coordination state 230. The initiate SAcoordination state 230 invokes a service migration state 232 at theserver agent, while the client agent returns to the link monitor state222. The service migration state 232 returns to the link monitor state222 once the migration of services is complete.

[0052] As previously mentioned, link connectivity can be ascertainedthrough access points as opposed to through network servers and/or otherMCUs. FIG. 9 illustrates a mobile communication system 240 comprising aplurality of logical networks or subnetworks coupled to a backbone 242to form a parent network 241 (e.g., internet, intranet). The mobilecommunication system 240 includes a first logical network 250 having anetwork server 252 and a second logical network 270 having a networkserver 284. A plurality of MCUs are associated with the logical networks250 and 270. The MCUs can move between logical networks and be re-homedemploying the intelligent homing agents in accordance with the presentinvention.

[0053] The first logical network 250 has a first MCU member 260 and asecond MCU member 264. The second logical network 270 has a third MCUmember 274 and a fourth MCU member 278. The first logical network 250includes a first access point 256 and a second access point 258, whilethe second logical network 270 includes a third access point 272 and afourth access point 282. Each access point serves as an entrance pointthrough which wireless communications can occur with the backbone 242and, thus the mobile stations and access points in the system 240. As isconventional, each MCU associates itself, typically by registration,with an access point coupled to the backbone 242, such that a link isformed between itself and other devices situated on the backbone 242.Each access point is capable of wirelessly communicating with otherdevices in the communication system 240 via respective antennas. Ageographic cell (not shown) associated with each access point defines aregion of coverage in which successful wireless communication can occur.Depending on the type of antenna selected, output power and RFsensitivity of the respective access point, the geographic cell may takeone of several different forms and sizes.

[0054] Each network server 252 and 284 include a server mobility agent(SA) 254 and each MCU includes a client mobility agent (CA) 262. Theserver mobility agents 254 and the client mobility agents 262collaborate with one another to re-home MCUs as they move from onelogical network to another. The client mobility agents 262 monitor linkmetrics associated with registration and deregistration with arespective access point to determine whether to become a member in a newlogical network or retain membership in a logical network. If a newaccess point is detected, it is determined if it is in a differentnetwork or in the same network. If the access point is in the samenetwork, the client mobility agent continues to monitor link metrics. Ifthe client mobility agent determines that the access point is in a newlogical network, the client mobility agent invokes a request for a newIP address to be assigned to the MCU. The new IP address can be providedusing standard available services such as DHCP. Once the client mobilityagent receives the new IP address, the new IP address can be associatedwith the MCU domain name using DNS or dynamically associated using DDNS.The domain name and IP address can be replicated across the networkutilizing directory services such as LDAP DS. The client mobility agent262 also initiates coordination with the new server mobility agent 254to transfer current open session information and to transfer services(e.g., e-mail, phone) associated with the MCU from the old network tothe new network.

[0055] In view of the foregoing structural and functional featuresdescribed above, methodology in accordance with various aspects of thepresent invention will be better appreciated with reference to FIGS.10-11. While, for purposes of simplicity of explanation, the methodologyof FIGS. 10-11 are shown and described as executing serially, it is tobe understood and appreciated that the present invention is not limitedby the illustrated order, as some aspects could, in accordance with thepresent invention, occur in different orders and/or concurrently withother aspects from that shown and described herein. Moreover, not allillustrated features may be required to implement a methodology inaccordance with an aspect the present invention.

[0056]FIG. 10 illustrates a methodology for transitioning MCUs betweengroups in accordance with an aspect of the present invention. Themethodology begins at 300 where at least one parameter associated withlink metrics is monitored. For example, the at least one parameter canbe source addressing, access point link connections, or signal quality.Source addressing and access point link connections can be used in a“Break-before-Make” mode, while signal quality can be employed in a“Make-before-Break” mode. It is to be appreciated that a variety ofdifferent link connectivity parameters in addition to the ones discussedabove can be employed in accordance with the present invention. Themonitoring can be achieved by using a client mobility agent residing ona MCU. The methodology then proceeds to 310.

[0057] At 310, the methodology determines if a new association has beendetected based on the at least one parameter associated with linkmetrics. If a new association is not detected (NO), the methodologyreturns to 300 to continue monitoring at least one parameter associatedwith link metrics. If a new association is detected (YES), themethodology advances to 320. At 320, the methodology determines whetherto join a new network. If the methodology determines that it is notdesirable to join a new network (NO), the methodology returns to 300 tocontinue monitoring at least one parameter associated with link metrics.For example, link connectivity of a new access point can be detectedsuch that a new association has been detected, but if the access pointis in the same logical network it would be desirable to remain in thesame logical network. Additionally, if link connectivity is detectedfrom more than one network, but the signal quality of the othernetworks, besides the one that the MCU is a member, has not reached apredetermined threshold then it would not be desirable to join any ofthose networks. Therefore, the MCU would remain a member of the currentnetwork. If the methodology determines that it is desirable to join anew network (YES), the methodology advances to 330.

[0058] At 330, the methodology determines if the transition betweengroups was a result of a “Make-before-Break” mode. If the methodologydetermines the transition between groups was a result of a“Make-before-Break” mode (YES), the methodology proceeds to 340. At 340,the methodology initiates a server agent coordination routine thatprovides the transfer of current communication sessions from the oldnetwork to the new network. The methodology then advances to 350. If themethodology determines the transition between groups was not a result ofa “Make-before-Break” mode (NO) (e.g., “Break-before-Make” mode), themethodology proceeds to 350.

[0059] At 350, a new address is requested for the MCU from the newlogical network. The request for the new address can be made, forexample, by invoking a DHCP request which will lease a new IP address tothe MCU. At 360, a new IP address is received and the old IP address isreleased. The methodology then proceeds to 370. At 370, the methodologyinitiates a server agent coordination routine that provides therelocation of store and forward services associated with the MCU to thenew logical network from the old logical network. The methodology thenreturns to 300 to repeat the monitoring of at least one parameterassociated with link metrics.

[0060]FIG. 11 illustrates a methodology for executing network servicesfor transitioning MCUs between groups in accordance with an aspect ofthe present invention. The methodology begins at 400 where a new addressrequest is received for an MCU desiring to join the logical group ornetwork. At 410, the methodology determines if a new address request isreceived. If a new address request is not received (NO), the methodologycontinues to monitor for a new address request. If a new address requestis received (YES), the methodology advances to 420. At 420, themethodology assigns a new address to the new MCU group member andupdates the domain name registration server to reflect the MCU domainname and IP address. A new IP address can be assigned using a DHCPservice, which then can update a domain name server repository table viaDDNS, such that the MCU is provided with a fully qualified domain nameand respective IP address associated with the fully qualified domainname.

[0061] At 430, the methodology determines if a coordination request isreceived from the MCU. If a coordination request is not received fromthe MCU (NO), the methodology returns to 400. If a coordination requestis received from the MCU (YES), the methodology advances to 440. At 440,a server agent to server agent coordination routine is initiated. Theserver agent to server agent routine can include one or more handshakingroutines to transfer information from the old network to the new networkwith respect to the new MCU group member. The current session (e.g., TCPsession, UDP session) is then transferred to the new logical network at450 if the transition is a “Make-before-Break” transition. At 460, thenew address is provided to the requester. The new address and fullyqualified domain name are then replicated to the other logical groups toprovide the groups in the overall network (e.g., intranet) with the newaddress and fully qualified domain name of the MCU at 470. Themethodology then proceeds to 480.

[0062] At 480, the services associated with the MCU are transferred tothe new logical group or network from the old logical group or network.This can include the assembling of a new electronic mailbox at the newlogical network and disassembly of the old electronic mailbox at the oldlogical network. Additionally, this can include the transfer of mailmessages from the old electronic mailbox to the new electronic mailbox.The methodology then returns to 400 to continue monitoring for newaddress requests.

[0063] What has been described above includes exemplary implementationsof the present invention. It is, of course, not possible to describeevery conceivable combination of components or methodologies forpurposes of describing the present invention, but one of ordinary skillin the art will recognize that many further combinations andpermutations of the present invention are possible. Accordingly, thepresent invention is intended to embrace all such alterations,modifications and variations that fall within the spirit and scope ofthe appended claims.

What is claimed is:
 1. A wireless communication system comprising: amobile communication unit having a client mobility agent that monitorslink metrics associated with communications between the mobilecommunication unit and logical network groups, the client mobility agentdetermines if a transition between logical networks is desirable basedon the monitored link metrics; and a server mobility agent thatcollaborates with the client mobility agent to transition the mobilecommunication unit from membership from an old logical network to a newlogical network upon invocation from the client mobility agent, themobile communication unit being assigned a new address corresponding tothe new logical network.
 2. The system of claim 1, the server mobilityagent being a first server mobility agent residing on a network serverof the new logical network. 3 The system of claim 2, further comprisinga second server mobility agent residing on a network of the old logicalnetwork, the first server mobility agent collaborating with the secondserver mobility agent to transfer services associated with the mobilecommunication unit from the old network to the new network.
 4. Thesystem of claim 3, the services being one of e-mail services and phoneservices.
 5. The system of claim 2, further comprising a second servermobility agent residing on a network of the old logical network, thefirst server mobility agent collaborating with the first server mobilityagent to transfer a current communication session associated with themobile communication unit from the old network to the new network. 6.The system of claim 5, the communication session being one of aTransmission Control Protocol (TCP) session and a User Datagram Protocol(UDP) session.
 7. The system of claim 1, the link metrics being sourceaddressing associated with link connectivity of the logical networks,the client mobility agent utilizes the source addressing to determine ifa transition between logical networks is desirable.
 8. The system ofclaim 1, the link metrics being signal quality associated with linkconnectivity of the logical networks, the client mobility agentutilizing the signal quality to determine if a transition betweenlogical networks is desirable.
 9. The system of claim 1, the clientmobility agent invoking a new address request from the new logicalnetwork upon selecting between logical networks.
 10. The system of claim9, the new address request being received and executed by a Dynamic HostConfiguration Protocol (DHCP) service residing on a network server ofthe new logical network, the DHCP service leasing a new InternetProtocol (IP) address associated with the new logical network to themobile communication unit.
 11. The system of claim 10, the clientmobility agent receives the new IP address and registers a domain nameand the new IP address with a Dynamic Domain Name Server (DDNS) service.12. The system of claim 11, a Lightweight Directory Access Protocol(LDAP) Directory Services (DS) replicating the registered domain nameand the new IP address with logical networks.
 13. The system of claim 9,the client mobility agent invoking a client agent to server agentcoordination routine, the client agent to server agent coordinationroutine invokes a server agent to server agent coordination routine thattransfers at least one of current session and current services from theold network to the new network.
 14. A mobile communication unitcomprising: a link monitor that monitors link metrics associated withcommunications between the mobile communication unit and logical networkgroups, the link monitor determines if a transition between logicalnetworks is desirable based on the monitored link metrics; and a networkinitializer that invokes a new address request from a new logicalnetwork if it the link monitor determines that a transition betweenlogical networks is desired.
 15. The mobile communication unit of claim14, the link metrics being source addressing associated with linkconnectivity of the logical networks, the link monitor using the sourceaddressing to support a Break-before-Make mode transition betweenlogical networks.
 16. The mobile communication unit of claim 14, thelink metrics being signal quality associated with link connectivity ofat least one logical network, the link monitor using the signal qualityto support a Make-before-Break mode transition between logical networks.17. The mobile communication unit of claim 14, the link metrics beingaccess point link connectivity of at least one logical network, the linkmonitor using the access point link connectivity to determine whether atransition between logical networks has occurred.
 18. The mobilecommunication unit of claim 14, the new address request being a requestfor a new Internet Protocol (IP) address associated with the new logicalnetwork.
 19. The mobile communication unit of claim 14, furthercomprising a server agent to server agent coordination routine that isinvoked prior to receipt of the new address associated with the newlogical network to collaborate the transfer of current sessioninformation and is invoked after receipt of the new address associatedwith the new logical network to collaborate the transfer of currentservices to the new logical network.
 20. The mobile communication unitof claim 14, the link monitor comprising a filter driver that monitorslink connectivity via a Local Area Network (LAN) driver and a DynamicLink Library (DLL) that provides an interface with a network serviceprocess and the filter driver, the network service process determineswhether a transition between logical networks is desirable based on thelink connectivity.
 21. A network server associated with a logicalnetwork for a mobile communication system that includes a plurality ofmobile communication units, the server comprising: a plurality ofnetwork services that provide new addresses associated with a logicalnetwork to mobile communication units requesting to join the logicalnetwork, the plurality of network services replicating the newlyassigned address to other logical networks; and a server mobility agentthat collaborates with a client mobility agent of the mobilecommunication unit to facilitate the transition of the mobilecommunication unit to the logical network.
 22. The server of claim 21,the server mobility agent collaborates with a server mobility agent of aprevious logical network which the mobile communication unit was amember to transfer current session information from the previous logicalnetwork to the logical network.
 23. The server of claim 21, the servermobility agent collaborates with a server mobility agent of a previouslogical network which the mobile communication unit was a member totransfer current services for the mobile communication unit from theprevious logical network to the logical network.
 24. The server of claim21, the plurality of network services comprising a Dynamic HostConfiguration Protocol (DHCP) service that provides a requesting mobilecommunication unit with a new Internet Protocol (IP) address associatedwith the logical network, a Dynamic Domain Name Server (DDNS) servicethat is dynamically updates a domain name of a mobile communication unitwith the new IP address and a Lightweight Directory Access Protocol(LDAP) Directory Service (DS) that replicates the domain name and new IPaddress to other logical networks.
 25. A wireless communication systemhaving a plurality of mobile communication units grouped into aplurality of logical network groups, the system comprising: means formonitoring link metrics associated with communications between a mobilecommunication unit and logical network groups; means for determining ifa transition of a mobile communication unit between logical networks isdesirable based on the monitored link metrics; and means for providing anew address for a mobile communication unit desiring a transition ofmembership between logical networks, the new address associated withmembership in a new logical network.
 26. The system of claim 25, furthercomprising means for replicating the newly assigned address to otherlogical networks.
 27. The system of claim 25, further comprising meansfor transferring services relating to a mobile communication unit to thenew logical network.
 28. The system of claim 25, further comprisingmeans for transferring current session information relating to a mobilecommunication unit to the new logical network.
 29. A method fortransitioning a mobile communication unit between logical networks, themethod comprising: monitoring link metrics associated withcommunications between a mobile communication unit and logical networkgroups; determining if a transition of the mobile communication unitbetween logical network groups is desirable based on the link metrics;requesting a new address for the mobile communication unit associatedwith the new logical network upon determining a desirable transition;associating the new address with a domain name of the mobilecommunication unit; and replicating the new address and associateddomain name to other logical network groups.
 30. The method of claim 29,further comprising transferring current session information to the newlogical network group.
 31. The method of claim 29, further comprisingtransferring services associated with the mobile communication unit tothe new logical network group.
 32. The method of claim 29, themonitoring link metrics comprising monitoring source addressesassociated with link connectivity of the logical networks.
 33. Themethod of claim 29, the monitoring link metrics comprising monitoringsignal quality associated with link connectivity of the logicalnetworks.
 34. The method of claim 29, the requesting a new addresscomprising executing a Dynamic Host Configuration Protocol (DHCP)service residing on the new logical network, the DHCP service leasing anew Internet Protocol (IP) address associated with the new logicalnetwork to the mobile communication unit.
 35. The method of claim 34,the associating a new address with the domain name comprisingregistering the new IP address and domain name with a Dynamic DomainName Server (DDNS) service.
 36. The method of claim 35, the replicatingthe new address and associated domain name to other logical networkgroups by employing Lightweight Directory Access Protocol (LDAP)Directory Service (DS) to replicate the registered domain name and thenew IP address to other logical networks.